A group of climate change activists who were convicted of conspiracy to commit aggravated trespass after they planned to shut down the UK's second largest power station walked free from court today.

The group were among more than 100 people arrested when police raided the Iona School in Sneinton, Nottingham, on the morning of Easter Monday, April 13, last year.

The protesters planned to trespass at the coal-fired Ratcliffe-on-Soar power station in Nottinghamshire and shut it down for a week, a trial at Nottingham Crown Court heard.

In December a jury found all 20 protesters, 18 of whom were sentenced today and who are from across the country, guilty of conspiracy to commit aggravated trespass.

Judge Jonathan Teare sentenced the group to a mixture of community orders and conditional discharges and told them the jury rejected their motive behind the aim of shutting down the power station.

He said: "There was substantial material before them that closure of the power station would not only stop the emission of carbon into the atmosphere, but also provide a huge publicity stage for your ambitions, and I join with the jury's verdict, having heard the evidence, that this was at least an equal aim of your intention to stop emissions.

"It is sad to reflect that this very expensive criminal trial has probably more than fulfilled your ambitions for publicity."

Prosecutor Felicity Gerry submitted to the judge an application for each defendant to pay costs of £5,000 which, she told the court, was a reduction of the rough figure of the £20,000 it cost per defendant to bring the case to court.

But Judge Teare ordered only two of the defendants to pay costs totalling £1,500 because many were on a low income or were claiming benefits.

He said: "Your actions - criminal actions - have cost the country hundreds of thousands of pounds in the police operation and investigation, and the subsequent criminal trial.

"I said at the conclusion of that trial that my main aim was to try and recoup some of the vast public expenditure. Sadly, my wishes are thwarted because nine of your number are either not in work or are living on public benefits, while the majority of the others are on modest incomes."

The court also heard how many of the defendants had previous convictions, the majority of which were for similar offences relating to environmental issues.

Martin Shaw, 46, who is in receipt of incapacity benefit, has four previous convictions ranging from criminal damage in 1983 to the same offence in 2007 when he jumped on a metal fence during a protest relating to GM crops.

Jacqueline Sheedy, 45, had six previous convictions dating from 1996, which included a conviction in Hackney in 2002 for disorderly behaviour after she threw a chocolate cake at a member of the Royal Family. Another, which was handed to her at Snaresbrook Crown Court in east London in 2006, was for obstructing a railway carriage, while a third, last March, was for aggravated trespass.

Judge Teare commended the group for their personal commitment to the environmental cause.

He said each of them received "glowing references" from peers or professionals and said: "If I may select some of the adjectives that recur throughout, they are these: honest, sincere, conscientious, intelligent, committed, dedicated, caring.

"You are all decent men and women with a genuine concern for others, and in particular for the survival of planet Earth in something resembling its present form."

During the trial the court heard the group said their invasion of the power station was necessary, but the prosecution said it was not and was "more fun" than more democratic means of protest.

At the start of the trial, Miss Gerry told the jury the activists planned to climb up into the chimneys at the power station, abseil inside them and stay there.

But she asked: "Is it really necessary to close down a power station when there are so many other democratic ways in which the message could be put across?

"Or did they do what they wanted to do because it was a great deal more fun, or because they did not have tickets to Glastonbury?"

She said that when police raided Iona School they found "extensive equipment for a large-scale operation", including food to last a week, climbing gear, sleeping bags, roll mats and ear and eye protection.

Officers also found a pre-written press release, entitled "Climate activists shut down Britain's second biggest power station", as well as a document prepared for workers at the power station.

But in an opening address to the jury, defence counsel Edward Rees QC said court figures from the European Union Environment Agency showed Ratcliffe-on-Soar, run by E.ON, produced 9,030,000 tonnes of CO2 in 2007, rising to 9,900,000 tonnes in 2008.

"This case, if anything, is about getting real," he said. "The rather hard facts you will hear about the situation that they believe we have got ourselves into.

"Equally, there will be no dispute that this was an organised plan to close down production of that elderly carbon-producing plant for a week."

Bradley Day, 23, of Spring Terrace, Swansea; Chris Kitchen, 32, of Dean Street, Brightlingsea, Colchester, Essex; and Daniel Glass, 27, of Willowbank Street, Glasgow, were each given a conditional discharge for two years.

Emma Sheppard, 29, of Hamilton Road, Manchester, was given a conditional discharge for 18 months and ordered to pay £500 costs.

Jesse Harris, 24, of Sholebroke Avenue, Leeds, and Jonathan Leighton, 21, of Willowbank Street, Glasgow, were each given a community order of 80 hours of unpaid work.

Olaf Bayer, 35, of Kent Road, Southampton, and Lisa Kamphausen, 26, of Highfield Crescent, Southampton, were both given a community order of 60 hours of unpaid work.

Jacqueline Sheedy, 45, of Foulden Road, London, was given a community order of 90 hours of unpaid work.

Clare Whitney, 25, of Catherine Street, Cambridge, was given a conditional discharge for two years and ordered to pay £1,000 costs.

Sarah Shoraka, 33, of Fairholt Road, London, and Ben Stewart, 36, of Alkham Road, London, will be sentenced at Nottingham Crown Court on January 18.